The best Shortbread in the World

I don't bother with mince pies or Christmas cake, even though I love them - I'm the only one that will eat them and I don't want to be mistaken for a snowball (not until after Christmas, anyway). But as everyone loves shortbread, I don't mind making a few big batches of this wonderful recipe from Jamie Oliver - very easy.
Preheat the oven to 150 degrees celcius. Butter a 9" square tin. Cream 250g butter and 3/4 cup of caster sugar until light & fluffy. Add 2 cups sifted plain flour and 1 cup of semolina, cornflour or rice flour (or combination) - whatever you have. Mix very lightly with a wooden spoon and then your hands until you have a smooth dough. Transfer to a floured surface and roll it out until it's about 1" thick all over. Press the dough into your tin, poking it into the corners with your fingers - don't worry about it looking perfect. Prick all over with a fork then stick it in oven for 50 mins until light golden. Sprinkle with more sugar while still warm. Allow it to cool slightly then cut into 12 chunky finger-sized pieces.
You can also add orange/lemon zest, vanilla essence or a bit of lavender to the dough for a yummy twist.